Heater/defroster for an automobile

ABSTRACT

Apparatus and Method for accelerating the warm-up of a heater/defroster in a passenger compartment of an automotive vehicle. A working fluid, such as power steering oil is rapidly heated by pumping it through a small orifice. An oil-to-coolant heat exchanger transfers heat from the working fluid to a liquid coolant. A blower generates an air stream and directs it across heat exchange surfaces of a coolant-to-air heat exchanger. Meanwhile the heated coolant is circulating through the interior of the coolant-to-air heat exchanger. This transfers heat from the liquid coolant and warms the air stream.

BACKGROUND OF THE INVENTION

[0001] This invention relates to heating systems for automotivepassenger vehicles. A principal object is to speed up the delivery ofheat to the heater and the windshield defroster on a cold day. Commonlyused prior art automobile heating systems rely upon heat generated inthe engine. This heat is transferred to a liquid coolant which is routedthrough a heater core located in the passenger compartment.

[0002] During normal operation of the vehicle the coolant is directedthrough a connected series of internal engine passages. These passagesare connected to a radiator which cools the engine by transferringexcess heat from the coolant to the outside environment. When the engineis started from an initially cold condition, it passes through an enginewarm-up phase during which the coolant bypasses the radiator. Thisconserves energy and speeds up the onset of smooth, normal operation.

[0003] On a cold day the engine warm-up phase continues for about 15minutes, the coolant is insufficiently hot for warming the passengers ordefrosting the windshield until after that period of time has elapsed.This is especially true for vehicles equipped with diesel engines. Inthe future, as engines become more efficient, smaller amounts of excessengine heat will be generated. This then will further prolong the enginewarm-up time.

[0004] Several methods are currently employed for decreasing vehiclewarm-up time. One such method involves using an electric heater in linewith the pre-existing heat exchanger. This arrangement decreases vehiclewarm-up time, but it requires a substantial increase in electrical powersupplied by the alternator. As a practical matter, the surpluselectrical power available for servicing such a heating system islimited to about 1.0 kw. Other known methods for increasing heat to thepassenger compartment include gas fired heaters, viscous shearingdevices, and electric seats.

SUMMARY OF THE INVENTION

[0005] This invention speeds up the operation of an automotive heatingsystem by providing a novel local heat generator in the form of anorifice of appropriate size. A working fluid, preferably an oil such aspower steering fluid, is heated by pumping it through the orifice at anappropriate mass flow rate. A 5-10 KW hydraulic pump is considered to besuitable for this purpose. The invention may be practiced through theuse a dedicated pump, but a shared pump also could be used. A suitableshared pump could provide pressurized hydraulic fluid flow for otherfunctions such as power steering, braking or radiator fan operation.Heat energy, delivered to the working fluid during passage through theorifice, is transferred to an airstream flowing through the passengercompartment, thereby warming the occupants and defrosting the windows.

[0006] In a first embodiment of the invention the working fluid is ahydraulic fluid, which flows through an oil-to-coolant heat exchanger,following passage through the orifice. As the working fluid passesthrough the oil-to-coolant heat exchanger, it heats a liquid coolantwhich is passing concomitantly therethrough. The liquid coolant flowsthrough a coolant-to-air heat exchanger situated in the passengercompartment. A blower fan then heats the passenger compartment byblowing ambient air across heat transfer surfaces in the coolant-to-airheat exchanger. Meanwhile the engine is being separately heated byanother flow of liquid coolant flowing in a loop which has a directreturn to the engine.

[0007] Further, in the first embodiment there is a thermostatic valvewhich directs the return flow of liquid coolant through a radiator whenthe engine has been heated to a suitably high operating temperature.There is also a bypass valve for isolating and circulating a fraction ofthe liquid coolant, independently of the main engine coolant circuit.This reduces the thermal mass of the liquid coolant used for heating thepassenger compartment, thereby increasing the speed of warm-up.

[0008] A second embodiment of the invention also uses hydraulic oil as aworking fluid. However, two heat exchangers are mounted in the passengercompartment; one of which exchanges heat from oil to air; and the otherof which exchanges heat from coolant to air. There is no heat exchangefrom oil to coolant. The two heat exchangers are positioned in tandem,so that air can be blown in sequence over the two sets of heat exchangesurfaces.

[0009] In a third embodiment of the invention an oil-to-air heatexchanger and a coolant-to-air heat exchanger are placed side-by-side.Air flow is provided by single blower and suitable ductwork.

BRIEF DESCRIPTION OF THE DRAWING

[0010]FIG. 1 is a sketch of an automobile heater/defroster according toa first embodiment of the invention.

[0011]FIG. 2 is a sketch of an automobile heater/defroster according toa second embodiment of the invention.

[0012]FIG. 3 is a sketch of an automobile heater/defroster according toa third embodiment of the invention.

[0013]FIG. 4 is a plot comparing the warm-up time for the presentinvention with the warm-up time for a typical prior art automobileheater/defroster.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014]FIG. 1 illustrates a preferred embodiment of the invention, ableto warm up output air from an automobile heater to a temperature ofabout 140 degrees Fahrenheit in about 3 minutes, based upon actualperformance measurements. The illustrated embodiment operates inassociation with an internal combustion engine 10 cooled by a liquidcoolant flowing through a series of internal passages (not illustrated)within the engine. A 50/50 mixture of ethylene glycol antifreeze and lowmineral content water will function satisfactorily as a coolant. Duringoperation at normal temperatures, the coolant flows from engine 10, viaa radiator supply line 23, to a radiator 12 where excess enginecombustion heat is absorbed and radiated to the atmosphere. A primarywater pump 14 maintains coolant flow through radiator 12 to engine 10,so long as the coolant temperature remains above some predeterminedminimum. This provides engine cooling, as required.

[0015] A thermostatic valve 16, connected as illustrated in FIG. 1,prevents coolant flow through radiator 12 so long as the temperaturethereof is below the predetermined minimum. A temperature sensor (notillustrated) causes thermostatic valve 16 to be switched to analternative position (connections for which may be understood byreference to FIG. 1), after the cooling liquid has reached thepredetermined minimum temperature. Thermostatic valve 16 operates in amanner known in the prior art to reduce engine warmup time by preventingearly heat loss through radiator 12.

[0016] The embodiment of FIG. 1 has a bypass valve 18 which can beswitched selectively between a first position and a second position,both of which may be understood by referring to the figure. In thecondition illustrated in FIG. 1 bypass valve 18 is in the first positionin which the coolant flowing through engine 10 is isolated from othercoolant flowing through a passenger compartment 400 (illustrated byphantom lines) via a coolant-to-air heat exchanger 24. In the secondposition coolant flow leaving engine 10 travels through valve 18 andheat exchanger 24 in which case heat from engine is transferred topassenger compartment 400 as is typical in present art. It will beunderstood that bypass valve 18 divides coolant between an Engine Loopand a Passenger Compartment Loop maintaining a relatively much smallervolume in the Passenger Compartment Loop. This reduces the thermal massof the liquid coolant used for heating the passenger compartment,thereby increasing the speed of warm-up.

[0017] Heat exchanger 24 comprises a conventional heater core, providedwith heat exchange surfaces (not illustrated) which remove heat from thecoolant flowing within distribution line 22 and transfer it to a streamof air generated by a blower 26.

[0018] A secondary water pump 34, powered by a motor 36, withdrawscoolant from a coolant storage vessel 32 and directs it via a secondcoolant supply line 42 to an oil-to-coolant heat exchanger 28. Coolantreturns from oil-to-coolant heat exchanger 28 to secondary water pump 34via second coolant distribution line 31, first coolant distribution line22, coolant-to-air heat exchanger 24, a second coolant return line 27and a third coolant return line 29.

[0019] While secondary water pump 34 is supplying coolant tooil-to-coolant heat exchanger 28, an oil pump 38 is withdrawing oil froman oil storage vessel 40 and supplying it to oil-to-coolant heatexchanger 28 via an orifice 44 and an oil distribution line 30.Preferably, oil pump 38 is of sufficient size to provide 5-10 KW ofhydraulic energy at vehicle idle conditions.

[0020] The task of oil-to-coolant heat exchanger 28 is to rapidly heatcoolant being supplied to coolant-to-air heat exchanger 24 during theperiod of time while engine 10 is warming up from a cold start. Heatexchanger 28 performs this task by withdrawing heat from oil flowingthrough oil distribution line 30 and transferring it into the flowingliquid coolant being pumped into line 42 by secondary water pump 34.Preferably oil-to-coolant heat exchanger 28 has a heat transfercapability of about 40 BTU/min-degrees Fahrenheit, and coolant-to-airheat exchanger 24 has a heat transfer capability of about 24BTU/min-degrees Fahrenheit. These heat transfer capabilities may beachieved by appropriate selection of heat transfer coefficients andsurface areas for the heat exchangers, as is well known in the art. Ablower rating of 150 cfm is satisfactory.

[0021] The oil provided by oil distribution line 30 may be powersteering oil, commercially available as Mopar MS-5391 or its equivalent.This oil is heated by resistance to flow through orifice 44. Flowparameters may be selected so as to provide a heating performance ofparticular interest. By way of example, orifice 44 may have a diameterof about 0.1 inch and may throttle oil flowing therethrough at a rate ofabout 10 gpm. This provides a pressure drop of approximately 2000 psiand generates heat at a rate of about 500 Btu/min. A suitable oil pump38 may be either a vane-type or a gear-type, having a displacement of4.2 cubic inches and a volumetric efficiency of 85%. Of course, the pumpmust have sufficient structural integrity for handling a head of 2000psi.

[0022] A heater/defroster configured as above described will heat theoil flowing through oil distribution line 30 to a temperature of 150degrees Fahrenheit in approximately one minute. The air blowing past theheat exchange surfaces of coolant-to-air heat exchanger 24 will rise toa temperature of 150 degrees Fahrenheit in approximately 2 to 3 minutes.FIG. 4 compares the computed performance of such a heater/defroster withtest results for a typical prior art system not equipped withtemperature boosting means according to this invention. As shown thereinby curve 50, the temperature of the heated air provided by thisinvention rises rapidly to about 170 degrees Fahrenheit in about 5minutes and then levels off. Curve 52 presents a corresponding plot oftemperature vs. time for a typical prior art system. This latter curveclimbs much more slowly to a maximum temperature of about 150 degreesFahrenheit in about 15 minutes. Clearly the invention provides asubstantial increase in passenger comfort on cold days, along with muchfaster windshield defrosting. A secondary benefit is a reduction inengine and transmission warm-up times. This system could be disabledduring normal operation to minimize energy consumption, or could bedisabled during times when quick acceleration is desired.

[0023]FIG. 2 illustrates a second embodiment of the invention. For easeof understanding, elements of FIG. 2 have like reference numerals ascorresponding elements in FIG. 1. The alternative embodiment of FIG. 2differs from the embodiment of FIG. 1 in its elimination of bypass valve18 and secondary water pump 34. Also, blower 26 warms the passengercompartment by blowing air over an oil-to-air heat exchanger 240 placedin front of a coolant-to-air heat exchanger 250. Oil pump 38 and orifice44 provide a supply of quickly heated oil for use in a fast warm-up ofthe air stream generated by blower 26. Thereafter the heat required forwarming the above-mentioned air stream is supplied by engine 10. Asmentioned above in connection with the embodiment of FIG. 1, primarywater pump 14 pumps liquid coolant through engine 10 and into coolantsupply line 20. Following warm-up, thermostatic valve 16 opens to permitcoolant flow through radiator 12. Heat exchanger 250 is substantiallysimilar to a prior art heater core. This embodiment could be implementedusing a 2-part heater core, with oil passing through one half, andcoolant through the other half.

[0024]FIG. 3 illustrates a second alternative embodiment which issubstantially similar to the first alternative embodiment of FIG. 2. Theprimary difference is that the heat exchangers 240, 250 are arrangedside-by-side rather than in tandem. This requires a damper door 360 andsuitable ductwork, as generally illustrated in the figure.

What is claimed is:
 1. Heating apparatus for a passenger compartment ofan automotive vehicle comprising: (a) means for blowing an air supplyinto said passenger compartment; (b) a first heat exchanger for heatingsaid air supply; and (c) a second heat exchanger for supplying heat tosaid first heat exchanger
 2. Heating apparatus according to claim 1wherein said second heat exchanger is an oil-to-coolant heat exchanger,and said first heat exchanger is a coolant-to-air heat exchanger.
 3. Inan automotive vehicle comprising a passenger compartment, acoolant-to-air heat exchanger, a blower for causing a stream of air toflow against said coolant-to-air heat exchanger and into said passengercompartment, and liquid coolant supply means for causing a heated streamof liquid coolant to heat said stream of air by flowing through saidcoolant-to-air heat exchanger in thermal contact therewith; theimprovement wherein said liquid coolant supply means comprises meansdefining an orifice, means for directing a flow of hydraulic oil towardsaid orifice, a pump for heating said hydraulic oil by forcibly pumpingit through said orifice, against a fluid resistance associatedtherewith, and an oil-to-coolant heat exchanger for transferring heatfrom said hydraulic oil to said liquid coolant.
 4. The improvement ofclaim 3 wherein said liquid coolant supply means comprises first coolantsupply means, connected for supplying liquid coolant to an engine ofsaid automotive vehicle, second coolant supply means connected forsupplying liquid coolant to said passenger compartment, and a bypassvalve for apportioning said liquid coolant between said first coolantsupply means and said second coolant supply means.
 5. The improvement ofclaim 4 wherein said first coolant supply means is and has capacity formaintaining a relatively much larger fluid volume than said secondcoolant supply, so that said passenger compartment may by warmed uprelatively quickly and independently of said engine.
 6. The improvementof claim 5 wherein said first coolant supply means comprises a radiatorfor removing heat from coolant flowing therethrough, a radiator supplyline for conveying heated coolant from said engine to said radiator,means for returning cooled coolant from said radiator to said engine,and a thermostatic valve for preventing the flow of said heated coolantthrough said radiator before said engine has warmed up to apredetermined operating temperature.
 7. Heating apparatus for apassenger compartment of an automotive vehicle comprising: (a) anoil-to-coolant heat exchanger; (b) supply means connected for supplyingan hydraulic oil to said oil-to-coolant heat exchanger; (c) an orificefor locally restricting passage of said hydraulic oil through saidsupply means; (d) a pump for heating said working liquid by forciblycausing said working liquid to flow through said orifice againstresistive forces generated thereby; and (e) heat transfer means fortransferring heat from said hydraulic oil to said passenger compartment.8. Heating apparatus according to claim 7, said heat transfer meanscomprising: (f) coolant supply means connected to provide a flow ofliquid coolant to said heat exchanger, so that said heat exchangertransfers heat from said working liquid to said liquid coolant; (g) ablower for generating an air stream in said passenger compartment; and(h) a coolant-to-air heat exchanger positioned in the path of said airstream so as to transfer heat from said liquid coolant to said airstream.
 9. Heating apparatus for a passenger compartment of anautomotive vehicle comprising: (a) an oil-to-coolant heat exchanger; (b)an oil supply vessel, connected for supplying hydraulic oil to saidoil-to-coolant heat exchanger and receiving a return flow therefrom; (c)an orifice for locally restricting passage of said hydraulic oil betweensaid oil supply vessel and said oil-to-coolant heat exchanger; (d) apump for heating said hydraulic oil by forcibly causing said hydraulicoil to flow through said orifice against resistive forces generatedthereby; (e) a coolant supply vessel, connected for supplying a liquidcoolant to said oil-to-coolant heat exchanger and receiving a returnflow therefrom, so that heat is transferred from said hydraulic oil tosaid liquid coolant; (f) a heater core positioned in said passengercompartment; (g) connecting lines connecting said heater core to saidoil-to-coolant heat exchanger for exchange of heat therebetween; and (h)a blower for causing air in said passenger compartment to flow acrosssaid heater core, thereby heating said air with heat extracted by saidheater core from said oil-to-coolant heat exchanger.
 10. Heatingapparatus according to claim 9, further comprising a water pump forcirculating said liquid coolant through said oil-to-coolant heatexchanger and through said heater core.
 11. In an automotive vehiclecomprising an engine provided with internal passages for circulation ofa liquid coolant, a first water pump for forcing a flow of said liquidcoolant through said internal passages, a radiator for removal of heatfrom said liquid coolant, a passenger seating compartment, a heater corepositioned in said passenger seating compartment, and a blower formaintaining a comfortable temperature by blowing air over said heatercore; the improvement wherein said automotive vehicle further comprisesa heat accelerator comprising an oil-to-coolant heat exchanger an oilsupply vessel, connected for supplying said hydraulic oil to saidoil-to-coolant heat exchanger and receiving a return flow therefrom, anorifice for locally restricting passage of said hydraulic oil betweensaid oil supply vessel and said oil-to-coolant heat exchanger, an oilpump for heating said hydraulic oil by forcibly causing said hydraulicoil to flow through said orifice against resistive forces generatedthereby, a coolant supply vessel, connected for supplying a said liquidcoolant to said oil-to-coolant heat exchanger and receiving a returnflow therefrom, so that heat is transferred from said hydraulic oil tosaid liquid coolant, and from said liquid coolant to said air.
 12. Theimprovement of claim 11, said heating apparatus further comprising asecond water pump for circulating said liquid coolant through saidoil-to-coolant heat exchanger and through said heater core.
 13. Theimprovement of claim 12 further comprising: a bypass valve, a coolantdistribution line extending between said bypass valve and saidcoolant-to-air heat exchanger, a first coolant supply line, extendingfrom said engine to said bypass valve, said bypass valve beingpositionable for selectively enabling passage of liquid coolant fromsaid engine to said coolant-to-air heat exchanger.
 14. Heating apparatusfor a passenger compartment of an automotive vehicle comprising: (a) anoil-to-air heat exchanger; (b) an oil supply vessel, connected forsupplying hydraulic oil to said oil-to-air heat exchanger and receivinga return flow therefrom; (c) an orifice for locally restricting passageof said hydraulic oil between said oil supply vessel and said oil-to-airheat exchanger; (d) a pump for heating said hydraulic oil by forciblycausing said hydraulic oil to flow through said orifice againstresistive forces generated thereby; (e) a coolant-to-air heat exchanger;(f) an internal combustion engine; (g) means for circulating a liquidcoolant through said internal combustion engine, so that said internalcombustion engine is cooled, and said liquid coolant is simultaneouslyheated; (h) means for conveying said liquid coolant from said internalcombustion engine to said coolant-to-air heat exchanger and returningsaid liquid coolant from said coolant-to-air heat exchanger to saidinternal combustion engine; and (i) means for blowing air into contactwith both of said heat exchangers and thence causing said air to flowinto said passenger compartment, so that said air is warmed by said heatexchangers and thereafter warms said passenger compartment. 15 Heatingapparatus according to claim 14, wherein said heat exchangers arearranged in tandem.
 16. Heating apparatus according to claim 14, whereinsaid heat exchangers are arranged side-by-side.
 17. A method of warminga stream of air for use in an automobile, said method comprising thesteps of: (1) heating an hydraulic fluid by pumping it at high pressurethrough an orifice (2) transferring heat from said hydraulic fluid to aheat exchanger; and (3) transferring heat from said heat exchanger tosaid stream of air.
 18. A method of warming a stream of air for use inan automobile, said method comprising the steps of: (1) heating anhydraulic oil by pumping said oil at high pressure through an orifice;(2) conveying said hydraulic oil from said orifice to an oil-to-coolantheat exchanger; (3) conveying a liquid coolant to said oil-to-coolantheat exchanger; (4) causing said oil-to-coolant heat exchanger totransfer heat from said hydraulic oil to said coolant; (5) conveyingsaid liquid coolant from said oil-to-coolant heat exchanger to acoolant-to-air heat exchanger; and (6) directing said stream of air intocontact with said coolant-to-air heat exchanger.